There has been a constant trend in the computer industry of packing more and more computer power into ever smaller spaces. Part of this trend includes larger random access memories in such computers. Many computers enable memory to be added to them by means of add-on memory cards. Usually such computers have attached to their bus one or more bus connectors into which such a memory, or other add-on card can be plugged. Usually a plurality of such connectors are placed next to each other so that a memory, or other add-on, card can be inserted in each. When this is the case, each such bus connector has associated with it what is known as a "card slot", that is, a pre-defined space into which such an add-on card can be inserted.
Such a card slot normally has a pre-defined length, width, and height. If the card exceeds the pre-defined length of the card slot, it will not normally fit within the card guides which are designed to hold the card at both ends. If a card inserted into such a bus connector sticks up out of the bus connector by more than the pre-defined height associated with the card slot, it may not fit in the bus connector's associated computer system. If the card is thicker than the dimension associated with the connector's slot, it may stick into the space of the slot associated with an adjacent connector, making it impossible to insert a card into that adjacent connector's slot. Thus, it can be seen that it is desirable to keep add-on cards within the pre-defined height, width, and thickness requirements established for the type of card slot into which it is to be inserted.
The problem, however, is that computer users want to pack ever larger amounts of memory into their computers. Since their computers usually only have a limited number of slots, that means there is a demand for memory cards which can pack a large amount of memory into the dimensions of a given card slot. To satisfy this need it has been common in the prior art to increase the density of memory boards by placing memory chips on both sides of such boards.
Another techniques, which has been used in the prior art to increase the density of memory boards, is to create memory boards which are actually comprised of two separate printed circuit boards, a so-called mother board, and a so-called daughter board, which is mounted on, and electrically connected to, the mother and daughters boards. Such a combination of mother and daughter boards provides an increased area upon which chips can be mounted, and thus increases the number of chips which can be included in a memory board, but it often results in a memory board which is too thick to fit within the width of an individual card slot. Such an oversized memory board, in effect, often ends up using the space allocated for two slots, and thus does not properly solve the problem of increasing the total amount of memory which can be placed in the limited number of slots which most computers have.
One of the reasons why prior art modules which include both mother and the daughter card are relatively thicken is the need to provide adequate cooling to the memory chips located between the mother and the daughter cards.
Another factor that traditionally adds thickness to such memory modules is the fact that daughter cards are traditionally attached to their mother cards by means of screws or nuts on the outside of the daughter cards. Unfortunately, these screws and nuts add to the overall thickness of the memory module.
Another factor which tends to decrease the amount of memory chips that can be placed on a given memory board or module is the fact that normally each separate pin of each separate memory chip has to have a separate electrical contact in the printed circuit board to which it is to be attached and soldered or otherwise electrically connected. The requirement of having a separate electrical pad for every pin on every chip not only increases the amount of surface area that is required to mount chips, but also increases the complexity of the electrical wiring contained within the printed circuit board on which such memory chips are mounted.